An introduction to muscle tissue

Movement is the fundamental characteristic of all animals. Animals move from one place to another place and it is brought about by a special soft, contractile muscle tissue. It also provides a framework for the body, definite posture and body support. It accounts for over 40% of the body weight.
The term muscle is derived from the Latin word” musculus” which means "little mouse”.
They are considered to be the machine of the body and are responsible for all types of body movements. Muscle is the only tissue in the body that has the ability to move other parts of the body through contraction.
They can contract or elongate and may become shorten or lengthen.
Each muscle has its own blood supply and has its own nerve connections.
The exact number of muscles in our body is difficult to define but the number may vary between 640 and 850. Among these, face alone has nearly 50 muscles and tongue consists of eight muscles. Nearly 17 muscles are involved in smile and 40 in frown.
Longest muscle is Sartorius—runs from outside of the hip, down and across to the inside of the knee. It helps to pull the thigh outward.
Smallest muscle is stapedius of inner ear – involved in hearing.
Biggest muscle is Gluteus Maximus or quadriceps femoris of buttock—helps in walking and running by pulling the leg backwards powerfully
Strongest muscle in our body is the masseter or jaw muscle and it is located on each side of the mouth.
Most active muscles are found in eye and they move more than 100,000 times a day.
Each muscle is an organ and it is made up of muscle tissue which in turn consists of a group of muscle cells.
Muscle cells are elongated and look like fibres. So, muscle cells are called muscle fibres.
Muscle develops by the fusion of embryonic mesodermal myoblast cells, by a process known as myogenesis. The embryonic mesoderm will be arranged on either sides of the developing spinal cord in the form of columns and they undergo segmentation to develop into structures called somites. Some of these somite cells differentiate into muscle tissue.
As age advances, muscle fibres decrease in number and the amount of connective tissue increases.  It results in loss of muscle and a decrease in muscle strength by 50% by the age 80. This type of age related muscle wasting leads to Sarcopenia.
Aging also leads to slowing of muscle reflexes and loss of muscle flexibility and it may cause decline in muscular performance.
Exercise increases the size and strength of each fibre,  causes increase in muscle tone, increase in the blood supply and thus increase the number of red blood cells. It lowers blood pressure and also increases respiratory and cardiovascular function.

Properties of Muscle Tissue:

Muscles exhibit properties like Irritability or Excitability, Contractility, Extensibility, Elasticity. They have the capacity to receive and respond to stimulus and can undergo contraction and relaxation.
Excitability - ability to be stimulated
Contractibility - ability to shorten and thicken
Extensibility - stretchable and extendable
Elasticity - Can recoil after being stretched and return to its original shape

Functions of Muscle Tissue:

The most distinguishing functional characteristic of muscles is their ability to transform chemical energy which is in the form of ATP, into mechanical energy. They function to produce force and motion.
The main functions of the muscular system are to produce movement, maintain posture, stabilize joints and generate heat.
Antagonistic muscles of the body are used for the movement of body parts. They function in pairs and antagonistically bring about movement i.e., one contracts, the other relaxes. Biceps and triceps muscles of the arm are such muscles which function in opposite directions to flex and extend the arm. Lever muscles to raise a body.
The other function of muscular system is the maintenance of posture and body position. Muscles often contract to hold the body still or in a particular position rather than to cause movement. The muscles responsible for the body’s posture contract to hold up the body in a particular position, sometimes even throughout the day without becoming tired.
They are also responsible for the movement of internal organs, such as the contraction of the heart and the movement of food through the food pipe, the movement of substances inside the body such as transporting substances like blood from one part of the body to another.
The final function of muscle tissue is the generation of body heat. Muscle contractions produce heat and help maintain normal body temperature. Active muscles produce heat and up to 70% of muscle energy can be lost as heat, raising body temperature.
Skeletal, cardiac and smooth muscles are three types of muscles found in animals.